Can Aphantasia be Objectively Measured?
Visualizing thoughts, past memories, or images of the future is ubiquitous in our daily lives. Still, the visualization experience is entirely unknown for a small group of people. Otherwise healthy people can completely lack the experience of visual imagery, a condition now referred to as aphantasia.
To determine whether someone has aphantasia or not, many researchers will conduct an initial evaluation using the Vividness of Visual Imagery Quiz (VVIQ), which asks you to rate the vividness of different scenarios to test the strength of your visual imagery. VVIQ is a proven psychometric for measuring individual differences in visual imagination and is considered a reliable self-assessment for identifying aphantasia.
Until recently, however, it was unclear to scientists whether people could not imagine visually or if they have images in their minds but are simply blind to them. To objectively address this question, a team of researchers from UNSW led by Dr. Joel Pearson conducted studies using Binocular Rivalry (BR) and a technique called perceptual priming.
Binocular Rivalry and How it Works
When our eyesight is blurry, it seems obvious that we would go get our eyes tested. It isn’t so easy when we suspect that the mental image inside our mind’s eye is hazy. Without objective measurement, it can be difficult to say for sure what is actually going on.
How can a doctor possibly see what is happening in someone else’s mind to the degree of accuracy needed to make a diagnosis? As far as aphantasia goes, scientists have actually found one way to test whether someone can visualize people, objects and settings in their mind’s eye. The technique, called perceptual priming, uses a phenomenon known as binocular rivalry.
When light enters our eyes, it sends information to our brains about what is happening in the world around us. The brain collects visual data from both eyes and essentially overlaps the information to show us one combined image of the world. However, the brain can get confused when both eyes receive completely different sensory information. At this point, rather than overlapping the images from both eyes, only one image will take dominance over the other, and that is the image that you will see.
This is known as a binocular rivalry – literally, two eyes competing. It is a phenomenon of visual perception in which perception alternates between different images presented to each eye.
For example, see the red and blue image of a horse below. If you look at the image through glasses where one lens is red and one lens is blue (like the old-school 3D glasses) and alternate between covering one eye at a time, the red horse will only be seen through the red lens and the blue horse through the blue lens. With both uncovered, your eyes will compete as to which color will be seen.
Some people will only see blue, while others will only see a red horse.
Interestingly, if you visualize the color blue in your head before the picture is shown to you, it becomes more likely that that is the picture and color you will see. This technique is known as ‘perceptual priming’ because it prepares or primes the brain to see that image or color. As you can probably guess, perceptual priming doesn’t work for aphantasics – they can’t visualize the color in their mind, so their brain won’t be primed, and they won’t be any more likely to see one image than the other.
To test for aphantasia, you can induce binocular rivalry at home and see if there is any correlation between perceptual priming and what you actually perceive. If you do not have aphantasia, you will be able to visualize the color and should find that you are more likely to physically see what you are visualizing in your mind’s eye. If you have aphantasia, then thinking about the color will not make it more likely that you will see it.
How to Conduct Binocular Rivalry Experiment at Home
You will need a pair of red-blue glasses. Old-school 3D theatre glasses should work! This will ensure that the red image will only make it through the red lens, and the blue image will only make it through the blue lens. This sends different sensory inputs to each eye and stimulates binocular rivalry.
Review the images of animals in this article, where two images of animals are superimposed over each other. One image is red, and the other is blue. Stabilize your head by resting your chin on something sturdy – a stack of books on your table works perfectly! Put on the glasses and scroll through the three images in this article. Then answer the following question:
Which image is more dominant red or blue?
Record your answers.
Once you have gone through all three images on this page, answer the following:
How many times did you see the red image, how many times did you see the blue image, and how many times was it unclear?
Record your results.
Next, conduct the same experiment again. Only this time, think about the color red. Try to imagine it in your mind if you can. Think of red things: Apples, Chili Peppers, Stop Signs, and Lava. Repeat the exercise while trying to imagine the color red.
Record your results.
Compare results between parts one and two.
How many times did you see the color red in part one? How many times did you see the color red in part two?
Share your results in the comments below.
Using Binocular Rivalry to Test for Aphantasia
If you found that you saw the red image more frequently in part two, then it is unlikely that you have aphantasia. This is because you have primed your brain to see the red image most of the time, a phenomenon that tends not to work on those with aphantasia.
Did you find it difficult, if not impossible, to visualize the color red in your mind in part two? If you couldn’t visualize the color in your mind, your brain was not expecting to see the red image in the same way as it would if you could visualize it. This means you saw results in part two that may have been pretty similar to part one. If that is the case, then this could mean you have aphantasia.
This simple experiment can provide you with more insight into your unique experience, but like any experiment, it is not perfect. The more times you do try it with different images, the more accurate your results will be. Try more examples. You can find more red and blue images here.
Did your results change or not change? A 7 or 8/10 times is usually a good indicator.
Binocular rivalry and perceptual priming are just one of many possible objective measures for evaluating mental imagery strength. Aphantasics will show almost no imagery-based rivalry priming. These results confirm that aphantasia is a lack of mental imagery and not a lack of metacognition.